Production of high quality light jet fuel



Jan. 2, 1962 F. G. CIAPETTA ET AL 3,015,549

PRODUCTION OF HIGH QUALITY LIGHT JET FUEL Filed June 4, 1957 nl, Wm. uw..

1N VE N TORS ihm/( faz/deba AW AT RN EY [lar/y l. Cad/radi Mil/ala [.'afufwr BY Patented Jan. 2, 1962 3,015,549 PRODUCTION OF HIGH QUALITY LIGHT JET FUEL This invention is directed to fuels utilizable in jet combustion devices. It is more particularly concerned with an improved process whereby there are produced jet fuels and aromatic hydrocarbons.

As is well known to those familiar with the art, the term jet combustion refers to a method of combustion wherein fuel is continuously introduced into and continuously burned in a conned space, for the purpose of deriving power directly from the hot products of combustion. The most complicated forms of jet engines presently proposed consist of a propulsion or jet tube, closed at one end, plus a gas turbine which extracts sufficient energy from the departing gases to drive the compressor. In present commercial forms, the compressor and turbine are assembled axially upon a common shaft, spaced far enough apart to permit a number of combu-stion chambers to be arranged about the shaft between the compressor and turbine, with an exhaust tube extending rearwardly from the turbine. The principal application of such engines is in powering aircraft, particularly for high-altitude operations. Therefore, the desiderata of fuels utilizable in jet combustion devices are many and varied.

As is well known to those familiar to the art, aromatic hydrocarbons such as benzene and `alkyl benzenes are highly desirable as solvents and as raw materials for numerous well known chemical processes. It is a feature of the present invention to provide valuable aromatic hydrocarbon fractions together with jet fuels of superior characteristics.

lt has now been found that the properties of jet fuels produced by hydrocracking a high boiling charge stock in the presence of the cracking catalyst preferably a platinum or palladium series metal catalyst can be markedly improved by a method that is simple and economical and which simultaneously provides substantial quantities ofvaluable aromatic hydrocarbons. It has been discovered that when the portion of a lower boiling range jet fuel, obtained by hydrocracking, that boils in the naphtha boiling range is replaced by a similar amount of parafnic raffinate produced by extracting a reformate from reforming straight-run naphtha, the properties of the jet fuel are greatly improved. It is also a feature of this invention that the aromatic extract of the reformate provides substantial quantities of valuable aromatic hydrocarbons.

Accordingly, it is an object of this invention to provide an improved jet combustion fuel. Another object is to provide a simple process for producing an improved lower boiling range jet fuel and valuable aromatic hydrocarbons. A further object is to provide a jet fuel of improved properties that is obtained by cracking in the presence of hydrogen and of a suitable hydrocracking catalyst. A specific object is to provide a jet fuel having improved properties that is obtained by cracking in the presence of a catalyst that contains a metal of the platinum or palladium series. Another specific object is to provide a method for producing improved jet combustion fuels and valuable aromatic hydrocarbons that involves cracking higher boiling charge stocks in the presence of hydrogen and of a hydrocracking catalyst replacing the portion of the hydrocracked jet fuel boiling in the naphtha boiling range with a paraffmic extract obtained from a reformate of straightrun naphtha and separating from the extract of said reformate a valuable aromatic hydrocarbon. A further specitc object is to provide jet combustion fuels that are produced by such process.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description considered in conjunction with the drawing which shows a schematic arrangement of a typical embodiment for carrying out a process of this invention.

In general, the present invention provides a method for producing a jet combustion fuel and aromatic hydrocarbons that comprises contacting a hydrocarbon charge stock with a hydrocracking catalyst in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge varying between about 2 and about 8O under hydrocracking conditions, to convert at least a portion of the hydrocarbon cha-rge into a jet fuel boiling within the range varying between about 160 F. and about 550 F.; separating said jet fuel into a cracked n-aphtha fraction and a fraction boiling at temperatures varying between about 390 F. and about 550 F.; separately reforming a straight-run naphtha in the presence of a reforming catalyst and under reforming conditions; separating the reformate into a parafnic fraction and an aromatic fraction; combining said parainic fraction with said fraction boiling at temperatures varying between about 390 F. and about 550 F. to produce a jet fuel and recoveringaromatic hydrocarbons from said aromatic fraction.

Throughout the specification and claims, dry gas refers to the methane, ethane, propane, and ethylene and propylene produced in a crackin-g process, expressed in terms of weight percent of the initial charge. Light naphtha boils in the range varying between about F. and about -225 F. The heavy naphtha fraction boils in the range varying between about 160-225 F. and about 350-425 F. The aniline-gravity product is expressed as the product of the A.P.l. gravity and the aniline number, as described in ASTM Test Methods D611 and D287. The smoke volatility index is obtained by adding to the smoke point (Method 2107 of Federal Specication VV-L-791) 0.42 times the volume percent of the fuel boiling under 400 F. The cracking activity of a carrier for the cracking catalyst used herein is expressed in terms of the percent, by volume, of a standard hydrocarbon charge which is cracked, under specific conditions, in the Cat A test. This test is described by Alexander and Shimp in National Petroleum News, 36, page R-537 (August 2, 1944). The unit for rating the cracking activity of such a carrier is called the activity index (A.I.).

The process of this invention will be understood from the figure which sets forth a schematic arrangement of a method for carrying out the process of the present invention. A suitable hydrocarbon charge is introduced through a pipe 10 and pumped by means of a suitable pumping device 11 through a pipe 12 into a heater 13. In the heater 13 a charge stock is heated to reaction temperature. The thus-heated charge then is passed through pipes 14 and 15 into a reactor 16.

Hydrogen gas, or a gas rich in hydrogen is introduced through a pipe 17 and pumped and compressed by means of a compressor 18.` The compressed hydrogen passes through a pipe 19 into a heat exchanger or heating device 20 wherein it is heated to reaction temperature. The thus-heated hydrogen is then commingled with the hydrocarbon charge in pipe 15 and the mixture then passes into the reactor 16. The reactor 16 can be a single reactor or comprise a plurality of reaction beds. In the reactor 16 there is contained a bed or plurality of beds of a suitable hydrocracking catalyst such as molybdenum oxide or platinum-containing catalyst as described hereinafter. The mixture of hydrogen and hydrocarbon charge is con- 3 tacted with the catalyst in the reactor -16 under suitable conditions to eifect at least partial conversion of the hydrocarbon charge into a lower boiling range jet fuel. It is understood, of course, that the degree of conversion used will depend upon the amount of jet fuel desired in a specific operation. In an extreme case, the entire charge material can be converted into jet fuels. The total eluent from the reactor 16 is removed through a pipe 21 and passed into a heat exchanger or suitable cooling device 22. In the heat exchanger 22, the eflluent is cooled to temperatures at which gaseous hydrogen can be separatedV from liquid phase. The thus-cooled effluent is passed through a pipe 23 into a high pressure separator 24.

In' the high pressure separator 24 there are a liquid phase and a gaseous phase. The gaseous phase containing substantial amounts of hydrogen is removed through a pipe 25 and can be recycled to the process through pipe 19. A liquid product from the high pressure separator 24 is removed through a pipe 26, passed through a depressuring zone 27 and thence through a pipe 28 into a suitable fractionating device 29.

In the fractionator 29, the liquid products are separated into suitable fractions. Dry gas is removed through a pipe 30. and can be sent to the gas processing plant. The butanes are removed through a pipe 31 and the light naphtha is removed through a pipe 32. The heavy naphtha is removed through a pipe 33. These materials removed via pipes 31, 32, and 33 can be utilized for the production of gasoline. A fraction boiling at temperatures within the range varying between about 390 F. and about 550 F. `is removed through a pipe 34. The material boiling at temperatures higher than about 550Q F. is removed -through a pipe 35. If desired, this material can be recycled to the process via pipe 12.

In a separate reforming operation, a straight-run naphtha is passed through a pipe 40 into a pumping device 41 and thence through a pipe 42 into a suitable heater 43. In the heater 43, the naphtha is heated to suitable reforming temperature. The thus-heated naphtha is passed through'a pipe 44 and 45 into a reforming unit 46. Hydrogen gas is introduced through a pipe 47 into a suitable pumping and compressing device 48. The compressed hydrogen then passes through aa pipe 49 into a heat exchanger or heating device 50 wherein it is heated to reaction temperature. The thus-heated hydrogen is then commingled with the hydrocarbon charge in pipe 45 and the mixture passes into Ilthe reforming unit 46.

The reforming unit 46 can be any reformingn system well known to those skilled in the art. Accordingly, it can comprise one or more fixed catalyst beds which may or may not be provided with intermediate reheaters. The unit may. also comprise a moving bed or a fiuidized bed type reactor. In the reactor 46, a naphtha and hydrogen are'contacted with a suitable reforming catalyst under reforming conditions. The reformate is withdrawn through pipe 51 and cooled by means of a heat exchanger or coolingdevice 52 to temperatures at which gaseous hydrogen can be separated from the liquid phase. The thus-cooled 1effluent is then passed through a pipe 53 into a high pressure separator 54 In the high pressure separator 54, there are a liquid phase and a gaseous phase. The gaseous phase containing substantial amounts of hydrogen is removed through a pipe 55 and can be recycled to the process to pipe 49. In most reforming processes, there is effected a net production of hydrogen. Accordingly, at least a portion of the hydrogen-richV gas withdrawn through pipe 55 can be cycled to the hydrocracking operation via pipe 55a to provide at least a portion of the hydrogen requirement thereof. The liquid product fromVv the high vpressure separator 54 is removed through a pipe 56 andV passed through andepressuring zone 57 and thence through a pipe 58 into an extraction device 59 In some cases, it will be desirable 1to` remove dry gas, butanes, and/or pentanes ref ormate before is subjected to extraction.

This can be done in a suitable gas separator (not shown).

In the extraction device 59, the reformate is separated into a raiiinate and extract phase by means of a suitable solvent. This is accomplished by introducing a solvent such as glycol or SO2 into the extractor 59 via a pipe 60. The solvents in contact with the reformate hydrocarbons extract an aromatic fraction that is removed through pipe 61 and passes into a separator 62. In the separator 62, a cut rich in aromatic hydrocarbons is removed through pipe 63 and the solvent is removed through a pipe 64 and can be recycled to pipe'60. The aromatic cut that is removed through pipe 63 can be utilized in a number of methods. It can be used as a raw material for the production of aromatic derivatives utilizing processes well known to the art. This fraction also has a very high blending octane number. Accordingly, it can be used as blending stock for the production of gasolines with a high performance number.

The raffinate obtained in extractor 59 is predominantly composed of parafiinic hydrocarbons. This raliinate is removed through a pipe 65 and passed into a separator 66 where any trace amounts of solvent that may be present can be removed. The paraiinic raffinate is then passed through a pipe 67 into a blending operation 68. In the blending operation 68 the fraction from the hydrocracking operation that is removed through pipe 34 is blended with the paratiinic rainate provided through pipe 67 to produce a high quality light jet fuel that is removed through pipe 69.

The jet fuels that are improved by the process of this invention are produced by cracking a gas oil in the presence of hydrogen and ofl suitable cracking catalysts. As is well known to those familiar with the. art, the jet fuels that are produced in the presence of various catalysts are not necessarily equivalent in their properties, i.e., some catalysts effect the production of jet fuels having better qualities and properties than those produced in the presence of certain other catalysts. In any` event, however, any jetfuel that has been produced by cracking in the presence of hydrogen can bei improved by means of the process of this invention.

A number of catalysts that are effective for cracking in the presence of hydrogen are known to the art. Suitable catalysts comprise a mixture of one or more compounds, preferably the oxides or suldes, of molybdenum, chromium, tungsten, vanadium, iron, nickel, and cobalt; and metallic nickel, iron and cobalt. Very often these materials are used on supports, such as acid treated clays, silica-alumina or other acidic oxides.,

As was disclosed in copending application, Serial No, 541,734, filed October 20, 1,955', superior jet fuels are produced by cracking in the presence of certain platinum and palladium series Vmetal-containing catalysts.

' The catalysts utilizable are those described in copending application, Serial No. 341,151., led on April 27, 17953, now abandoned; and in the continuationfin-part thereof, Serial No. 418,166,7filed on March 23, 1954. Briey, these catalysts comprise between about 0.05 percent, by weight, and about 20 percent, by weight of the final catalyst, preferably between about 0.1 percent and about 5 percent, by weight, of the metals of the platinum andv palladium series, i.e., those having atomic numbers of44-46, inclusive, 76-78, inclusive, supported upon synthetic composites of two or more refractory oxides. The carrier is a synthetic composite of two or more oxides of the metals of groups IIA, IIIB- and IVA and B of the periodic arrangement ofY elements [1. Chem. Ed., 16', 409 (1939)]. These synthetic composites of refractory oxides must have an activity index of at least about 25. They can also contain halogens and other materials which are known in the art as promoters for cracking catalysts, or small amounts of alkali metals that are added for the purpose of con-V trolling the activity index of the carrier; Non-limiting examples o f-the composites contemplated hereinu include Sitka-alumina., siliafzfcone. slisafalrmin-zitwn? alumina-boria, silica-alumina-uorine, and the like. The preferred support isra synthetic composite of silica and alumina containing between about 1 percent, by weight, and about 90 percent, by weight, of alumina. These synthetic composites of two or more refractory oxides can be made by any of the usual methods known to those skilled in the art of catalyst manufacture. Examples of methods of preparing them are set forth in copending applications, Serial Numbers 351,151 and 418,166, referred to hereinbefore.

The following example illustrates a method of preparing a platinum-containing catalyst utilizable in the process of this invention:

EXAMPLE 1 A synthetic silica-alumina carrier or support containing percent, by weight, alumina was prepared by mixing an aqueous solution of sodium silicate (containing 158 g. per liter of silica) with an equal amount of an aqueous acid solution of aluminum sulfate containing 39.4 g. Al2(SO4)3 and 28.6 g. concentrated H2504 per liter. The mixture was dropped through a column of oil wherein gelation of the hydrogel was effected in bead form. The bead hydrogel was soaked in hot water (about 120 F.) for about 3 hours. The sodium in the hydrogel was then removed by exchanging the gel with an aqueous solution of aluminum sulfate [1.5 percent A12(SO4)3 by weight] containing a small amount (0.2 percent by weight) of ammonium sulfate. The thus-exchanged hydrogel bead was water-washed. Then, it was dried in superheated steam (about 280-340o F.) for about 3 hours and, finally, calcined at".1300" F. under a low partial pressure of steam for about 10 hours. The silica-alumina beads were then crushed to pass through a lll-mesh screen and the material retained on a 25-mesh screen (U.S. standard screen series) was used for catalyst preparation.

APortions of the crushed, calcined carrier were then barely covered with aqueous solutions of chloroplatinic acid, of concentrations sul'licient to produce the desired amount of metal in the finished catalyst. The excess solution was removed by centrifuging. The thus-impregnated carrier was then heated in a covered vessel at 230 F. for 16 hours. The catalyst was heated in N2 to 450 F. and treated with hydrogen for 2 hours at 450 F. Then, it was activated in hydrogen for 2 hours at 900 F. before it was used. The catalyst thus-prepared contained 0.47% platinum, by weight of the catalyst. The silica-alumina carrier had an activity index of 46.

The cracking operation used in the process of this invention is carried out in the presence of hydrogen in amounts, expressed as the molar ratio of hydrogen to hydrocarbon charge, varying between about 2 and about 80, preferably between about 5 and about 50. The liquid hourly space velocity will vary between about 0.1 and about l0, preferably between 0.1 and about 5. When the aforedescribed platinum or palladium series metal catalysts are used, the cracking temperature will vary between about 500 F. and about 825 F., preferably between about 600" F. and about 775 F. The hydrogen pressure can vary between about 100 p.s.i.g. and about 3000 p.s.i.g., preferably between about 350 and 2000 p.s.i.g. When the cracking operation, however, is carried out in the presence of other type catalysts, such as the oxides and suldes of the various metals listed hereinbefore, the temperature for cracking are higher. Thus, in cracking in the presence of hydrogen with such catalysts, temperatures from between about 600 F. and about 1200n F. are required and, generally, pressures in the order of 50G-10,000 p.s.i.g. must be used.

The charge stocks contemplated for use in the process of this invention are hydrocarbon fractions that have an end-boiling point greater than about 650 F. These materials can have initial boiling points of 400 F. or higher. Accordingly, the stocks contemplated include a light gas oil which boils between about 40G-550 F. and G50-750 F., a heavy gas oil which boils between about 600-650 F. and about SGO-900 F., and a vacuum gas oil boiling between about SOO-850 F. and about 1l00-1200 F. lt must be understood, however, that the charge can overlap the foregoing boiling ranges. It can even span other ranges that include, for example, medium and heavy gas oils. Another material that is utilizable herein is a whole topped crude that has been deasphalted. This material is the entire portion of the crude remaining after the light ends have been removed by distillation. Such a fraction, therefore, will boil between about 400 F. up to 1100-1200 F. and higher. Refractory cycle stocks obtained from conventionally cracked stocks are also contemplated. These materials usually boil between about 400 F. and about 850 F.

The presence of even relatively small amounts of nitrogen compounds in the charge stock may interfere with the process of this invention. For relatively short terms of operation, the presence of nitrogen in amounts of as much as about 0.12 percent, by weight, and higher can be tolerated in the charge. When operating with such charge stocks, however, it is necessary to resort to intermittent operation. The nitrogen compounds also reduce catalyst activity, thus necessitating higher reaction temperature. This produces a more aromatic and less suitable jet fuel.

Charge stocks that contain about 0.1 percent nitrogen, or less, can be cracked in a continuous operation, over long periods of time, without a loss in catalyst activity. Accordingly, the cracking charge stocks should contain less than about 0.1 percent nitrogen, by Weight, when continuous operation is desired with the platinum or palladium catalysts. Preferably, the nitrogen content should be less than about 0.08 percent, by weight. With certain other catalysts excessive nitrogen compounds cause aging and similar precautions must be taken.

In cases in which continuous operation is contemplated and the cracking charge stocks contain more than 0.1 weight percent nitrogen, the nitrogen content should be reduced to an amount less than about 0.1 weight percent, and preferably, below about 0.08 weight percent, before charging to the process. The reduction in nitrogen content can be effected by any of the methods well known in the art, such as, for example, acid treatment, propane deasphalting, and hydrogenolysis under high pressure, in contact with catalysts such as molybdenum or tungsten oxide, nickel tungsten sulde, cobalt molybdate, cobalt tungstate, etc. As indicated hereinbefore, somewhat higher nitrogen contents can be tolerated, if the operation is intermittent or of relatively short duration. Also, a higher nitrogen content can be tolerated in the charge provided that more severe operating conditions, such as higher temperatures, are employed.

The reforming charge stocks contemplated in the process of this invention are the straight-run naphthas distilled from crude petroleum. The naphtha charge can, of course, be obtained from any crude source. However, a particular advantage of this process is that highly parafiinic naphthas may be advantageously used. Usually highly paraflinic naphthas are undesirable reforming charge stocks because low yields are obtained when reforming is carried out under severe conditions to produce the high octane number gasoline required for modern engines. In this invention the paranic extract is utilized as hereinbefore described in jet fuel. Further, as described herein, the less paraiiinic hydrocracked naphtha can be used to produce gasoline of high octane number in high yield. The straight-run naphtha charged to the reformer should have an initial boiling point of about -225 F. and an end point of about BOO-450 F. With some catalysts the nitrogen content should desirably be less than about 2 p.p.m. and preferably less than 1 p.p.m. In some cases, the sulfur content lshould desirably be less than 20 p.p.m. Straight-run naphthas 7 may be pretreated catalytically by any of the well known processes before reforming.

The catalysts utilizable in the reforming operation are well known to those skilled in the art. Thus, the catalysts can be oxides or suldes of the metals of groups IV, V, VI, VII and VIII of the periodic arrangement of the elements, alone or, as is generally the case, supported upon a carrier, such as alumina, spinels, etc. Such catalysts include molybdenum oxide, chromium oxide, cobalt molybdate, and the like. The reforming conditions used with these catalysts include, usually, temperatures of 750- 1150 F. and pressures of 50-3000 p.s.i.g.

It is also contemplated to carry out the reforming operation in the presence of hydrogen and of platinumor palladium-containing catalysts. Such catalysts contain between about 0.05 percent and about 2 percent, by Weight of the catalysts, of platinum or palladium, or both, deposited upon supports. Suitable supports, or carriers, include mixtures of two or more refractory oxides, such as silica-alumina, silica-alumina-thoria, alumina-borra, etc. Another type of support proposed for platinum reforming catalysts is alumina that may have halogen composited therewith, and which may also contain small amounts of silica. An especially preferred catalyst is described in copending application, Serial No. 420,092, filed yMarch 31, 1954, now Patent No. 2,849,378. This catalyst comprises platinum or palladium deposited upon silica having composited therewith small amounts of alumina, wherein the amount of alumina is correlated with the surface area of the catalyst and with the method of preparing it. The reforming conditions used with these platinumor palladium-containing catalysts include temperatures varying between about 700 F. and about 1000 F., preferably between about 725 F. and about 950 F. The liquid hourly space velocity will vary between about 0.1 and about 10, preferably between about 0.5 and about 4. The hydrogen pressure will vary between about 100 p.,s.i.`g. and about 1000 p.s.i.g., preferably between about 200 and about 500 p.s.i.g. The molar proportion of hydrogen to hydrocarbon charge will be between about 1 and about 20, preferably between about 4 and about 12.

A number of processes for separating aromatic hydrocarbons lfrom non-aromatic hydrocarbons in naphtha fractions are well known to those familiar with the art. Generally -known processes are reviewed, for example, in Petroleum Processing for August 1955 at pp. 1162- 3 and 1197-1202. Typical solvent extraction methods and suitable solvents therefor are described in United States Letters Patents Nos. 2,688,645 and 2,773,918. In general, the methods utilizable include (l) sulfur dioxide extraction, (2) extractive distillation with phenol, (3) silica gel adsorption and (4) solvent extraction. The preferred solvents for solvent extraction methods are diethylene glycol and triethylene glycol. Other sol- Vents, however, can be used, such as 1,3-butanediol; 1,4 butanediol; ,-oxydipropionitrile; and ethylene carbonate. Specific processing methods and conditions are well known to those skilled in the art.

v The following examples are for the purpose of demonstrating the process of this invention and of illustrating the effectiveness thereof. It is to be-strictly understood that the present invention is not to be limited to the specific catalysts and charge materials described in the examples ork to the specific operations and manipulations involved. As is described hereinbefore, other catalysts and charge stocks and operations can be used and are considered to be within the scope of the present invention.

EXAMPLE 2 A Mid-Continent naphtha had the following properties:

8 ASTM distillation, F.:

I.B.P. 207 10% 228 30% 241 70% 285 323 -E.P. Y 360 This material was subjected to reforming in the presence of hydrogen and of a catalyst comprising platinum supported upon alumina. The reforming operation is carried out in the presence of hydrogen in amounts, expressed as the molar ratio of hydrogen to hydrocarbon charge, of about 10, using a hydrogen pressure of about 500 p.s.i.g., a liquid hourly space velocity of 1.66, and a temperature of 940-950 F. Under these conditions there was obtained a yield of 83 volume percent of depentanized 98 O.N. reformate having the properties set forth in Table I.

The reformate thus obtained was extracted in four stages with 11.8 volumes of diethylene glycol in a Podbielniak centrifugal extractor operated at 3000 r.p.m. The pressure used was -180 p.s.i.g. The extraction was carried out at a temperature of 96 F., employing a solvent-tooil volume ratio of 11 and Va throughput of 63 gallons of reformate Vplus solvent per hour. There was thus obtained a high para'inic raflinate (37.4 volume percent) having the properties set forth in Table I. The extract (62.6 volume percent) was yfreed of solvents 'and was found to have the properties set forth in Table I.

Table 1 Reformate Rafnate Extract Gravity, API 46. 9 63. 2 33. 8 ASTM Distillation, F

I.B.P 196 187 228 5%. 201 205 251 50%- 250 241 287 90%. 326 318 339 E P 394 389 390 Octane No., F-l (clear) 88.0 46.0 1 115.6 Octane No., F-l-l-3 ce. TEL 97. 5 76. 0 l 127.0 Paratns, Wt. Percent 41 -84 8 Naphthenes, Wt. Percent- 2 5 2 Aromatics, Wt. Percent 57 1l 90 Benzene 0.3 3.9 Cy-Alkylbenzene 0. 7 21. 7 Cs-Alkylbenzene- 2. 4 34. 1 Cg-Alkylbenzene- ;4. 2 23. 5 Cw-Alkylbenzene 2. 7 5. 9 CwAlkylbenzene 0. 7 0. 7

1 Performance number.

EXAMPLE 3 A Kuwait gas oil had the following properties:

API gravity 39.1 ASTM distillation, F.:

I.B.P. i 418 50% 506 E.P. 634 Sulfur, weight percent 0.94

This gas oil was subjected to cracking in the presence of the catalyst described in Example 1. The pressure used was 1000 p.s.i.g., the hydrogen-to-oil ymolar ratio was 40 and the liquid hourly space velocity was 0.5. The cracking operation was carried out at -a tempera- 9 ture of 670 F. There was thus produced about 70.8 volume percent of a .TP-4 type jet fuel having the properties set forth in column 3 of Table II.

It was found that about 50 volume percent of this jet fuel was comprised of naphtha boiling in the range varying between about 170 F. and 390 F. This naphtha was separated from the material boiling at temperatures higher than about 390 F. The parainic raflinate described in Example 2 was added to the total hydrocracked product boiling above about 390 F. This blend was then distilled to-a 480 F. end point to produce a modified jet fuel. This modi-tied jet fuel contained about 45 volumes of raffinate and 55 volumes of 390 F. plus hydrocracked product. There was thus obtained an improved jet fuel having the properties set forth in column 3A of Table II.

EXAMPLE 4 The charge stock used in the run of this example was a distilled oil obtained by cracking a gas oil mixture obtained predominantly from a West Texas crude in a conventional thermofor catalytic cracking unit using a silicaalumina catalyst. This charge material had the follow- This gas oil was subjected to cracking in the presence of the catalyst described in Example 1. The pressure used was 1000 p.s.i.g., the hydrogen-to-oil molar ratio was 40 and the liquid hourly space velocity was 0.5. The cracking operation was carried out at a temperature of 735 F. There was thus produced about 78.5 volume percent of a .IP-4 type jet fuel having the properties set forth in column 4 of Table II.

It was found that about 67 volume percent of this total jet fuel was comprised of naphtha boiling in the range varying between about 170 F. and 390 F. This naphtha was separated from the material boiling at temperatures higher than about 390 F. The paraflnic raflinate described in Example 2 was added to the total hydrocracked product boiling 'above about 390 F. This blend was then distilled to a 480 F. end point to produce a modified jet fuel. This modified jet fuel contained about 68 volumes of raffinate and about 32 volumes of 390 F. plus hydrocracked product. There was thus obtained an improved jet fuel having the properties set forth in column 4A of Table Il.

Table II Gravity, API 50. 6 55. 7 45. 6 56. 5 ASTM Distillation, F

I.B.P 220 194 210 176 306 258 286 227 389 398 360 286 465 460 460 448 513 478 532 470 Freezing Point, F -65 -60 -76 -76 Aromatics, Vol. Percent (FI 3.2 4. 3 21. 8 12. 1 Sulfur, Wt. Percent 0. 026 V 0022 0. 004 0. 0012 Aniline-Gravity Product--. 8. 040 8, 960 5, 470 7, 730 Smoke Point 39. 0 40. 0 20. 0 27. 0 Smoke Volatility Index 62. 5 61. 4 47. 7 58. 5

It will be noted, from the data set forth in Table II, that by means of the blending operation of this invention, there is obtained a jet fuel that has vastly improved characteristics over those of the original hydrocracked fuel. The most notable and important improvement lies in the increase in the Aniline Gravity Product which is a measure of the amount of energy in the fuel. The hydrocracked naphtha that was separated in Examples 3 and 4 can be subjected to a reforming operation to produce high octane gasoline. Indeed, it has been found that by reforming a hydrocracked naphtha, greater overall yields of reformate and greater yields of hydrogen can be experienced than when reforming a straight-run naphtha from the same crude source. This is fully described and illustrated in copending application, Serial No. 582,732, now abandoned.

Although the present invention has been described with preferred embodiments, it is to be understood that moditications and variations may be resorted to, without departing from the spirit and scope of this invention, as those skilled in the art will readily understand. Such variations and modifications yare considered to be within the purview and scope of the appended claims.

What is claimed is:

1. A process for producing a jet combustion fuel and aromatic hydrocarbons that comprises contacting a hydro- -carbon charge stock having an initial boiling point of at least about 400 F. and an end boiling point greater than about 650 F. with la catalyst comprising between about 0.05 percent and about 20 percent, by weight of the catalyst, of at least one noble metal of the platinum and palladium series deposited upon a synthetic composite of refractory oxides of at least two elements of groups IIA, IIIB and IVA Aand B of the periodic arrangement of elements having an activity index of at least 25, in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge varying between about 2 and about 80, at pressures varying between about p.s.i.g. and labout 3000 p.s.i.g., at a liquid hourly space velocity varying between about 0.1 and about 10, 'and at temperatures varying between about 500 F. and about 825 F., to convert atleast a portion of the hydrocarbon charge into a jet fuel boiling within the range varying between about F. and about 550 F.; separating said jet fuel into a cracked naphtha fraction and a lfraction boiling at temperatures varying between about 390 F. and about 550 F.; separately reforming a parafnic straight-run naphtha in contact with a platniumcontaining reforming catalyst, in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge, varying between about l and about 20, at pressures varying between labout 100 p.s.i.g. and about 1000 p.s.i.g., at a liquid hourly space velocity varying between about 0.1 and about l0, and at temperatures varying between about 700 F. and about 1000 F. to produce a reformate; separating said reformate into a paraflim'c fraction and an aromatic fraction; combining said paratinic fraction with said fraction boiling at temperatures varying between about 390 F. and about 550 F. to produce a jet fuel and recovering aromatic hydrocarbons from said aromatic fraction.

2. A process for producing a jet combustion fuel and aromatic hydrocarbons that comprises contacting a hydrocarbon charge stock having an initial boiling point of at least about 400 F. and an end boiling point greater than about 650 F. with a catalyst comprising between about 0.1 percent and about 5 percent, by weight of the catalyst, of platinum deposited upon a synthetic composite of silica and alumina having an activity index of at least 25, in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge varying between about 5 and about 50, at pressures varying between about 350 p.s.i.g. and about 2000 p.s.i.g., at a liquid hourly space velocity varying between about 0.1 and about 5, and at temperatures varying between about 600 F. and about 775 F., to convert at least a portion of the hydrocarbon charge into a jet fuel boiling within the range varying between about 160 F. and about 550 F.; separating said jet fuel into a cracked naphtha fraction and a fraction boiling at temperatures varying between about 390 F. and about 550 F.; separately reforming a paranic straightrun naphtha in contact with a platinum-on-alumina reforming catalyst, in the presence of hydrogen in amounts, expressed in molar ratio of hydrogen to hydrocarbon charge varying between about 4 and about l2, at pressures varying between about 200 p.s.i.g. and about 500 p.s.i.g.,

at a liquid hourly space velocity varying between about 0.5 and about 4, and at temperatures varying between about 725 F. and about 950 F. to produce a reformate; separating said reformate into a parainic fraction and an aromatic fraction by extraction with diethylene glycol; combining said parafnic fraction with said fraction boiling at temperatures varying between about 390 F. and about 550 F. to produce a jet fuel and recovering aromatichydrocarbons from said aromatic fraction.

3. The process dened in claim 2, wherein said hydrocarbon charge stock having an initial boiling point of at least about 400 F. and an end boiling point greater than about 650 F. is a Kuwait gas oil; and said parainic straight-run naphtha is a Mid-Continent naphtha.

4. The process defined in claim 2, wherein said hydrocarbon charge stock having an initial boiling point of at least about 400 F. and an end boiling point greater thanV about 650 F. is a refractory cycle stock; and said parafnic straight-run naphtha is a Mid-Continent naphtha.

5. A process for producing a jet combustion fuel and aromatic hydrocarbons Vfrom a hydrocarbon charge stock boiling above about 400 F., which comprises: converting said charge stock at least'in part into a jet fuel boiling within the range about 160 F. to about 550 F. by hydrocracking said charge stock Vin the presence of a catalyst with hydrocracking activity at a temperature within the range about 500 F. to about 1200" F., at a hydrogen pressure within the range about 100 p.s.i.g. to about 10,- 000 p.s.i.'g. and in the presence of lhydrogen in an amount such Vthat the molar ratio of hydrogen to hydrocarbon charge is Within the range about 2 to about 80; separating said jet fuel boiling within the range about 160 F. to about 550 F. into a cracked naphtha fraction and a fraction boiling within the range about 390 F. to about 550 F.; separately reforming straight run naphtha by contacting said naphtha with a catalyst having reforming activity at a temperature within the range about 700 F. to about. 1150 F. `and at a hydrogen pressure within the range about 50 to about 3,000 p.s.i.g. to produce a reformate and hydrogen; and separating said reformate .into a parafiinic fraction and an aromatic fraction; and combining said paratinic fraction with said fraction boiling within the range 390 E. to about 550 F. to produce a jet fuel.,

6. The process of claim 5 further limited to said hydrocarbon charge stock having an initial boiling point greater than about 400 F. and an end boiling point of at least about 650 F.

References Cited in the le of this patent UNITED STATES PATENTS V2,749,225 Barnum et al June 5, 1956 2,763,623 Haensel Sept. 18, 1956 2,768,126 Haensel et al. Oct. 23, 1956 

1. A PROCESS FOR PRODUCING A JET COMNUSTION FUEL AND AROMATIC HYDROVARBONS THAT COMPRISES CONTACTING A HYDROCARBON CHARGE STOCK HAVING AN IONTIAL BOILING POINT OF AT LEAST ABOUT 400*F. AND AN END BOILING POINT GREATER THAN ABOUT 650*F. WITH A CATALYST COMPRISING BETWEEN ABOUT 0.05 PERCENT AND ABOUT 20 PERCENT BY WEIGHT OF THE CATALYST OF AT LEAST ONE NOBLE METAL OF THE PLATIUM AND PALLADIUM SERIES DEPOSITED UPON A SYNTHETIC COMPOSITE OF REFRACTORY OXIDES OF AT LEAST TWO ELEMENTS OF GROUPS IIA, IIIB AND IVA AND B OF THE PERIODIC ARRANGEMENT OF ELEMENTS HAVING AN ACTIVITY INDEX OF AT LEAST 25 IN THE PRESENCE OF HYDROGEN IN AMOUNTS EXPRESSED IN MOLAR RATIO OF HYDROGEN TO HYDROCARBON CHARGE VARYING BETWEEN ABOUT 2 AND ABOUT 80, AT PRESSURES VARYING BETWEEN ABOUT 100 P.S.I.G. AND ABOUT 3000 P.S.I.G. AT A LIQUID HOURLY SPACE VELOCITY VARYING BETWEEN ABOUT 0.1 AND ABOUT 10, AND AT TEMPERATURES VARYING BETWEEN ABOUT 500* F.AND ABOUT 825*F., TO CONVERT AT LEAST A PORTION OF THE HYDROCARBON CHARGE INTO A JET BOILING WITHIN THE RANGE VARYING BETWEEN ABOUT 160*F. AND ABOUT 550F., SEPARATING SAID JET FUEL INTO A CRACKED NAPTHA FRACTION AND A FRACTION BOILING AT TEMPERATURES VARYING BETWEEN ABOUT 390*F. AND ABOUT 550*F., SEPARATELY REFORMING A PARAFFINIC STRAIGHT-RUN NAPTHA IN CONTACT WITH A PLATNIUMCONTAINING REFORMING CATALYST IN THE PRESENCE OF HYDROGEN IN AMOUNTS EXPRESSED IN MOLAR RATIO OF HYDROGEN TO HYDROCARBON CHARGE, VARYING BETWEEN ABOUT 1 AND ABOUT 20, AT PRESSURES VARYING BETWEEN ABOUT 100 P.S.I.G. AND ABOUT 1000 P.S.I.G. AT A LIQUID HOURLY SPACE VELOCITY VARYING BETWEEN ABOUT 0.1 AND ABOUT 10, AND AT TEMPERATURES VARYING BETWEEN ABOUT 700*F. AND ABOUT 1000*F. TO PRODUCE A REFORMATE; SEPARATING SAID REFORMATE INTO A PARAFFINIC FRACTION AND AN AROMATIC FRACTION; COMBINING SAID PARAFFINIC FRACTION WITH SAID FRACTION BOILING AT TEMPERATURES VARYING BETWEEN ABOUT 390*F. AND ABOUT 550*F. TO PRODUCE A JET FUEL AND RECOVERING AROMATIC HYDROCARBONS FROM SAID AROMATIC FRACTION. 